Counterbalancing means for lift bridges



June 2, 1928. 1,673,358

S. HARDESTY COUNTERBALANCING MEANS FOR LIFT BRIDGES Filed Feb. 17, 1927 2 Sheets-Sheet 2 erion rninen Hanmis'rit, or LitnonIirour, new Yonir, assua e to witness: is

nannsscry, or new roan, r, A W- nnnLL AND MYsnLr.

ooranritnastxrr oonsrs'rrno or was A. L.

coUN'rERBALAuoING Means roe LIFT B'nrnens'.

Application filed. February 17, 1927. Serial No. 168,860.

Lift bridges of various sorts which are [TOilllt'OiI'WQlQilted are subject to a variation in the counterhalancing loads as the span rises and falls.

The invention herein described ail'ns to counterbalance these varying loads or strains.

The accompanying drawings illustrate en'ibmliincnts of the intention.

in. 1 a side elevation of a vertical lift bridge;

2 is a side elevation of one end ot the rith a modified counterbalancin'g arrau gemen t.

. The lift span and other moving parts are shown in full linesin the lowered position of the bridge and in dotted lines in the raised position. The span 1 moves vertically be tween towers Various arrangements of iuotor and connections are used for lifting and lowering such" spans. These are not illustrated inthe presentcase. The weight or" the lift span is taken olii the motor by means of cables 3 leading from the ends of the span up to pulleys 4- atthe tops of the towers and over such pulleys and down to counteiwvei rhts 5. As the span rises the length of the innerportionot the cable 3 is essencd and the length of the outer portion, the end connected to the counterweight, is incrca l, so, that the uplifting or counterbz'ilancinrgetlect increases. And conversely, on the dhwnward movement of the span the connterbaiancing load decreases.

The main counterbalancing cables are of considerable weight and there is consequent 1y a considerable variation in the load on the motor.

According to this invention, such variation ot the loads on the span is counterbalanced in whole or in part. For this purpose the vertical movement of the span is utilized to change the direction oi a stress applied to it by siu iplementary coun'terbalancing means; such change in direction being accompz'mied by a change in the vertical. component of the stress or load. The principle may be applied in a great variety of ways.

According to Fig. 1, supplementary counterbalancing cables 6 are connected to the top chord of the span at points somewhat distant from the ends and lead over pulleys 7 near the tops of the towers and down to suppleinentary counterweights 8. The number and dimensions of these supplementary counterweight-lug devices will be adjusted according to the weights of the span and the main counter-weights and their cables. In the lowered position of the span, the strain on the cable 6 is nearly vertical. The vertical component or lifting effect on the span is,

therefore, nearly equal to'the weight of the counterweight 8. In the highest position'ot' the span, the cable 6 is nearly horizontal; and the vertical component of the pull on the span is very slight. The difference be tween the Vertical components in the two extreme positions may be made equal to the variation in the pull of the main counterweights the pull from the supplementary counterweight decreasing as that from the main counterweight increases. c

According to Fig. 2, the main counter- Weighting system is the same as tor-Hg. 1, but the supplementary scheme is different. Cables 9 are connected to the span 1 near its end and are led through guide blocl'rslO to pulleys 11 tastenedon the towers 2 at points betwen the extreme lower and upper positionsof the span. [The relativelocatio'n of the guide pulley 11 and the point of connection of the cable to the lift span ensures an even greater change in the direction inwhich the pull of the counterweight is applied to the spanthan in Fig. 1. In the latter the pull is applied always upward and with a varyingdegree of obliquity; in Fig. 2, the pull of the supplementary counter'weights is upward duringa part of the rise of the lifting span. and actually downward during the remainder. There are various other ways in whicha stress can be applied to the lift span in different directions as the latter rises.

The main countcrbalancinn schemes illustrated are in etlcot parts of theliftin'g ap paratus. Various other lifting means may be used which impose varying loads on the co unterbal ancin g span as it rises, and such variations may be counterbalanced completely or to the desired extent by the present invention. In tac t, whenever there is a variation on the load of the lift span in rising, the present improve ment may be used to counterbalance it. In fact, Where the arrangementis such as to exert an upward pull on the lift span at all times, merely changing the directions and the vertical components of such pull, as in Fig. 1 for example, the Weights 8 and cables 6 may Ill be so proportioned and arranged as to eliminate the main counterweighting systenrreferred to. The weights 8 in that case would have a counter-balancing eflect to the full extent desired in the lower position of the span and as the cables 6 run over the pulleys and provide an increased load, tending to lift the span, such increase would be counterbalanced by the change in the direction of application of the load and the consequent diminution in the vertical component of the applied stress.

The same counterweight principle may be applied to various other structures having heavy parts which are moved up and down in straight vertical lines like the vertical letti bridge illustrated. And it will he understood that the drawings herein are chiefly diagrammatic and that where two weigl'its 8 with their cables are shown. there may be any number of such units arranged at locations where the strains can be best applied to the lift span: and that the same holds true in the application of the invention to other structures.

Various modifications may be made by those skilled in the art without: departing from the invention as defined in the following claims.

hat: I claim is:

1. A lift bridge including in combination a pair of towers a vertical lift span which rises in a straight line between said towers, main counterbalancing means acting on the ends of the span and imposing varying loads on it as it rises and supplementar; means separately connected to the span for counterbalancing such variation.

2. A lift bridge including in combination a pair of towers, a vertical lift span between said towers, main counterbalancing means comprising cables connected to the ends of the span and running over supports on said towers and carrying counterweights and supplementary means for counterbalancing the variation in the load imposed on the span by said cables as the span rises. said supplementary means comprising cables separately connected to the ends of the span and carrying counterweights.

3. A vertical lil t bridge including in com hination a lift span which rises in a. straight line and counterbalancing means for applying a pull in ditterent directions to the span as the latter rises.

.l. A vertical lift. bridge including in combination a lift span which rises in a straight line, a counterweight, a cable leading therefrom over a guide to a point on the span, the guide and said point being so located with relation to each other as to apply the pull of the cable to the lift span in ditl crent directions as it rises.

5. A. vertical lift bridge including in combination a lift span which rises in a straight line and countcrweighting means comprising a weight and a cable leading therefrom over a guide to a point on the lift: span outside of the vertical line through the guide so as to apply the pull to the span in ditl'erent directions as the span rises.

6. A vertical lift lu'idge including in combination av li'tt span which rises in a straight line and lifting means therefor adapt d to impose arying loads on the span as it rises and counterbalancing means for applying a pull in different directions to the span as the latter rises.

7. A vertical lift bridge including in combination a lift. span which rises in a. straight; line having a main counterbalaneing system which imposes varying loads on t'he span as it. rises and s1ipplementaiy countel-balancing means for applying a pull in different directions to the span as it rises.

8. Counterbalancing apparatus for lift bridges or the like having a rising part which moves upward in a straight line, said cminterbalancing apparatus comprising means for applying a pull to the rising part of the structure in different directions as it rises.

9. Counterbalaneing apparatus for litt bridges or the like having a rising part which moves upward in a straight line. said counterbalancing apparatus comprising a weight and a cable leading therefrom over a guide and to the rising part of the structure, the guide and said point being so located with relation to each othe as to apply the pull of the cable to said rising part in different directions as it rises.

10. Countcrbalancing apparatus tor lift bridges or the like having a IlSlIlg part which moves in a straight line. said counterbalancing apparatus comprising a weight and a cable leading therefrom over a guide and to a point on the rising part of the structure which is outside of the vert ieal line through the guide so as to apply the. pull to said part in ditl'erent directions as it rises.

Tn witness whereof, I have hereunto signed my name.

SHORTKIDGE l-lAl-(DESTY.

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